Chinenfabrik



Unrrnn Srerss PATENT @rsrcni EDUARD LUHMANN, OF ANDERNACH, ASSIGNOR TO THE SllR'llllER MAS- I OHINENFABRIK, VORMALS H. HAMMERSOHMIDT, OF SUETH, NEAR OO- LOGNE, GERMANY.

PROCESS OF MAKlNG PURE CARBONlC-ACID GAS.

fiPEGIFICATION forming part of Letters Patent No. 491,365, dated February 7, 1893.

Application filed August 8,1892. Serial No. 42,609. (No specimens.)

To a3?) whom it may concern.-

Be it known that I, Ennnno LUHMANN, a subject of the King of Prussia, German E111 peror, and a resident of Audernach-on-the- Rhine, Kingdom of Prussia, German Empire, have invented a new and useful Improved Process for Producing Pure Carbonic-Acid Gas, of which the following is an exact specification.

The invention has for its object an improved process for producing carbonic acid gas in a purecondition and is characterized by the employment of the phosphates of an alkali.

The method as hitherto used for producing carbonic acid gas from substances forming or giving olit' carbonic acid either by decomposition or by combustion, consists in causing the carbonic acid arising therefrom to be ab sorbed by a soda lye or carbonate of soda, thus forming bicarbonate of soda, and in heating the lye subsequently thereby expelling the carbouicacid gas, which is conveyed to a gasometer in order to be liquefied. This method however of forming bicarbonate and carbonate of soda is very costly, on account of the prolonged boiling required for the complete decomposition of the bicarbonate; a great amount of heat being thereby consumed in this usual process.

I have ascertained that a very convenient substitute for alkali lye and carbonate of alkali is found in the phosphates of alkali, and more particularly in the phosphate of soda. When carbonic acid proceeding from a coke furnace, or natural springs or evolved in the course of chemical processes, is'led into a solution of phosphate of soda in cold water acid phosphate of soda is formed, besides bicarbonate of soda, and this mixture of acid phosphate and bicarbonate of soda is com pletely reconverted into phosphate of soda by the application of amoderate heat, somewhat below boiling point.

It will be obvious that phosphate of soda altords an excellent means for absorbing pure carbonic acid from impure gaseous mixtures and for liberating again this carbonic acid gas in an easy manner by the application of heat. As an example, I state the proportion in which the phosphate of soda may be used: Ten pounds of phosphate of soda (Na HPOQ are dissolved in one hundred pounds of water, I then lead into the cold solution the impure carbonic acid (proceeding from any source) care being taken that the temperature of this said gas is as low as possible. An absorption of the carbonic acid (00 then takes place, and the chemical reaction is repre sented by the equation:

It will be seen that acid phosphate of soda (NaH PO and bicarbonate of soda (Nal'lCO are formed thereby. \Vhen the chemical action is complete, the mixed solution of acid phosphate and bicarbonate of soda resulting therefrom is heated by means of asteam-coil (not perforated) the temperature employed being 212 Fahrenheit, as amaximum by the application of which heat pure carbonic acid is obtained, which is hereafter collected in a gasometer.

The chemical reaction is illustrated equation:

that is to say the solution has returned to its initial state, and when cooled, may be used again for the absorption of impure carbonic 8o acid gas, as described.

I Wish to be understood that, although I by preference employ phosphate of soda, I do not confine myself to the employment of this salt, as I may also employ the phosphates of 85 potash, or pyrophosphates and the like.

Having thus fully described the nature of my invention, What I desire to secure by Letters Patent of the United States is:-

l. The method of obtaining pure carbonic 9o acid gas consisting in introducing the gases containing carbonic acid into a solution of a phosphate of alkali and in thereafter liberating the absorbed carbonic acid gas by heating the mixed solution resulting therefrom 9 5 for the purpose as described.

by the 2. The method of obtaining pure carbonic In testimony whereof I have signed this acid gas consisting in introducing the gases specificationin the presence of two subscribcontaining carbonic acid into a solution of a ing witnesses.

phosphate of soda and in thereafter liberat- EDUARD LUHMANN. 5 ing the absorbed carbonic acid gas by heating Witnesses:

the mixed solution, resulting therefrom, for FRITZ SCHROEDER, the purpose as described. SIBILLA LANG. 

